Immobilization of uranium(VI) in a cementitious matrix with nanoscale zerovalent iron (NZVI)

• Published in: Chemosphere (Oxford) 2019-01, Vol.215, p.626-633
• Main Authors: Sihn, Youngho, Bae, Sungjun, Lee, Woojin
• Format: Article
• Language: English
• Subjects: Adsorption; Carbonates - pharmacology; Cement; Cementation; Ferric Compounds - chemistry; Humic Substances; Iron - chemistry; Nanoscale zerovalent iron; Photoelectron Spectroscopy; Solidification; Stabilization; Sulfides; Surface Properties; Uranium; Uranium - chemistry; Uranium - isolation & purification
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2018.10.073

We developed a novel solidification and stabilization process using a nanoscale zerovalent iron (NZVI)-cement system for reductive immobilization of hexavalent uranium (U(VI)) in a soil–cement matrix. The NZVI suspension without cement demonstrated high removal efficiency (100% in 2 h) and fast removal kinetics (53.7 Lm−2d−1), which surpassed those of other Fe-containing minerals (i.e., green rust, mackinawite, magnetite, and pyrite). Significant removal of aqueous U(VI) was observed in NZVI-cement slurries and minimal adsorbed U was desorbed by a bicarbonate/carbonate (CARB) solution. Surface analysis using scanning electron microscopy and X-ray photoelectron spectroscopy revealed U distributed homogeneously on the surface of the NZVI-cement and transformed considerably from U(VI) to reduced U species by coupled oxidation of Fe(0)/Fe(II) to Fe(III). Furthermore, the increase in pH and NZVI concentration, and presence of humic acid resulted in the enhanced U(VI) reduction in NZVI-cement slurries. The NZVI-cement system was tested with a soil matrix, resulting in successful immobilization of aqueous U(VI) in both batch and column experiments. Moreover, the U(VI) removed in the NZVI-cement system was not leached out by the CARB solution during long-term experiments. The results suggest an NZVI-cement system could represent a promising remediation alternative for effective and stable immobilization of U(VI) in contaminated sites. [Display omitted] •A permeable NZVI-cement matrix is developed for solidification/stabilization of U(VI).•NZVI showed higher U(VI) removal than other Fe(II)-containing minerals in the matrix.•U(VI) was reductively immobilized in the NZVI-cement slurries system.•NZVI concentration, pH, and humic acid significantly influenced the U(VI) reduction.•Effective U(VI) removal was observed in a NZVI-cement-soil column.